Contrast Sensitivity testing has proven to be a useful tool for probing basic mechanisms of vision. It has been shown to have diagnostic value for a number of neuro-ophthalmological disorders. Contrast sensitivity testing of patients has revealed visual deficitis which were not evident from measuring visual acuity (Bodis-Wollner and Camisa, 1980). The usefulness of this measure is limited, however, because it can assess visual functioning only at threshold. Unlike the artificial testing situation in a laboratory or a clinic, normal visual experience occurs within the suprathreshold contrast range. Contrast matching is a psychophysical technique now used in the laboratory to study suprathreshold vision. This technique consists of asking an observer to adjust the contrast of a test stimulus so that it appears equal to the contrast of a standard stimulus. The primary aim of this study is to investigate visual functioning within the suprathreshold contrast range, in normal subjects and in patients with various types of neuro-ophthalmological disorders described as having low vision. To accomplish this, a contrast matching paradigm will be used, and the efficiency of this method as a clinical tool will be evaluated. We plan to analyze the processing of four of the most cricital aspects of vision, those of spatial frequency, temporal frequency, stimulus orientation, and lateral interactions between neighboring regions in the visual field.